Originally Posted by Tangerine
It has to sit out for quite a while to spoil. Like a couple of days. I never let my rice sit out, though. I just put it in the fridge and heat it in the microwave when I want to finish it. But I have seen rice that sat out too long. Not something you would want to put in your mouth, that's for sure!
That's not actually true, it only take a couple of hours for the toxins to be of a level to cause illness. The toxins are also not killed during reheating.
The issue with rice is that the bacteria is spore forming as I mentioned, this means that it needs to be heated to around 112C to be killed (with the boiling point of water being 100C, the high temperature needed doesn't usually get reached during cooking). At around 60C and below 5C the bacteria puts on a little jacket (or forms a spore) to protect itself from the suboptimal conditions, but when it's jacket comes off it starts to release toxins which can't be removed by reheating. These toxins are the real problem, not so much the bacillus cereus itself. The toxins aren't released in the rice packaging as the rice is dry which is another type of suboptimal condition for the bacteria to live in, so once again on goes it's little protective jacket until it gets nice and warm and wet (such as after it's been cooked).
Pre-cooked packaged rice is treated with extreme caution. Usually there are no people involved in the packaging of it, it's all done in a controlled environment by machines. The rice is blasted at 112C before being packed with nitrogen 'just to be safe'.
Advice to people who save rice tends to be that if it has been in the danger zone for 4 hours or more it should be disposed of as it is too high risk to eat. As DarkGinger said it is a risk not a certainty as the offending bacteria is not always present, but it's a risk that I sure don't take. Rice is also not the only place this bacteria can be found, however it is the most common place that is it found.
Hope that clears things up BDH.